Many known agrochemicals have shown to be more effective in combination than when applied individually.
Herbicides, and in particular glyphosate, are usually sprayed in combination with organic adjuvants (such as surfactants acting as wetting agents and stickers) and inorganic adjuvants (such as inorganic nitrogen containing fertilizers). The presence of the various adjuvants guarantees good phytoactivity and avoids detrimental and/or unpredictable effects due to local conditions (water hardness, soil quality, weather conditions etc).
Among the several documents reporting combinations of adjuvants we cite:
U.S. Pat. No. 6,852,674, which describes a herbicidal mixture comprising a benzoyl derivative, a fertilizer containing nitrogen and an organic adjuvant;
U.S. Pat. No. 6,479,437, which describes a herbicidal mixture of a 3-heterocyclyl-substituted benzoyl derivative, a nitrogenous fertilizer and an organic adjuvant;
EP 058 4227, which reports a herbicidal composition comprising a effective amounts of a substituted cyclohexanedione, at least one nitrogen containing fertilizer that is present in an amount that increases the herbicidal activity of the substituted cyclohexanedione and one or more organic adjuvants;
EP 498 145, which reports glyphosate solid compositions comprising at most 10% of water, and discloses that the combination of an ammonium salt with alkyl polyglycosides enhances the phytoactivity of the glyphosate in a notably, nonexpected manner.
Unfortunately, inorganic nitrogen fertilizers are solid salts with limited solubility in water and herbicides may be poorly soluble in water. This is particularly the case for the combination of ammonium sulfate and glyphosate, which is well known to partially crystallize from its aqueous solution even when dosed for proper phytoactive application on the field in diluted form.
The addition of various surfactants to the aqueous ammonium sulfate solutions has been proposed to avoid crystallization and, eventually, to further increase the biological activity of the glyphosate.
US RE36,149 describes the preparation of a homogeneous and stable aqueous ammonium sulfate blend with a non ionic alkyl polyglycoside.
The amount of ammonium sulfate in the solution is reported to be about 8.5 pounds (3.145 Kg) for about 2.5 gallons (9.475 l) of the blend, corresponding to about 27% by weight of ammonium sulfate.
The blend is then mixed in locus with a solution of glyphosate and sprayed on the weeds.